Blood Vessels and Circulation Chapter 21, part 1 Blood Vessels and Circulation

Learning Objectives Distinguish among the types of blood vessels. Describe fluid and dissolved material transport into and out of the cardiovascular system. Describe the factors that influence blood pressure and blood pressure regulation. Discuss the mechanisms involved in the movement of fluids between capillaries and interstitial spaces.

Learning Objectives Describe how blood flow and pressure in tissues is regulated. Identify the principle blood vessels of each circuit and the areas they serve. Describe fetal circulation patterns and the changes that occur in these patterns at birth and during aging.

SECTION 21-1 The Anatomy of Blood Vessels

Structure of vessel walls Walls of arteries and veins contain three distinct layers Tunic intima Tunica media Tunica externa

Figure 21.1 A Comparison of a Typical Artery and a Typical Vein

Differences between arteries and veins Compared to veins, arteries Have thicker walls Have more smooth muscle and elastic fibers Are more resilient

Arteries Undergo changes in diameter Vasoconstriction – decreases the size of the lumen Vasodilation – increases the size of the lumen Classified as either elastic (conducting) or muscular (distribution) Small arteries (internal diameter of 30 um or less) are called arterioles

Capillaries An endothelial tube inside a basal lamina These vessels Form networks Surround muscle fibers Radiate through connective tissue Weave throughout active tissues Capillaries have two basic structures Continuous Fenestrated Flattened fenestrated capillaries = sinusoids

Figure 21.2 Histological Structure of Blood Vessels

Figure 21.4 Capillary Structure

Capillary Beds An interconnected network of vessels consisting of Collateral arteries feeding an arteriole Metarterioles Arteriovenous anastomoses Capillaries Venules

Figure 21.5 The Organization of a Capillary Bed Figure 21.5a, b

Veins Collect blood from all tissues and organs and return it to the heart Are classified according to size Venules Medium-sized veins Large veins

Venous Valves Venules and medium-sized veins contain valves Prevent backflow of blood

Figure 21.6 The Function of Valves in the Venous System

Distribution of blood Total blood volume is unevenly distributed Venoconstriction maintains blood volume Veins are capacitance vessels Capacitance = relationship between blood volume and pressure PLAY Animation: Anatomy Review: Blood Vessel Structure and Function

Figure 21.7 The Distribution of Blood in the Cardiovascular System

SECTION 21-2 Cardiovascular Physiology

Circulatory Pressure Circulatory pressure is divided into three components Blood pressure (BP) Capillary hydrostatic pressure (CHP) Venous pressure

Figure 21.8 An Overview of Cardiovascular Physiology

Resistance (R) Resistance of the cardiovascular system opposes the movement of blood For blood to flow, the pressure gradient must overcome total peripheral resistance Peripheral resistance (PR) is the resistance of the arterial system

Overview of Cardiovascular Pressures Factors involved in cardiovascular pressures include Vessel diameter Cross-sectional area of vessels Blood pressure Blood viscosity

Figure 21.9 Relationships among Vessel Diameter, Cross-sectional Area, Blood Pressure, and Blood Viscosity Figure 21.9